Increasing the octane of olefinic gasolines using disproportionation alkylation and reforming steps

ABSTRACT

A process for converting an olefinic gasoline to a higher octane value gasoline comprises the steps of subjecting the feed gasoline, or a fraction thereof, to olefin disproportionation in the presence of added ethylene to convert some of the heavier olefins to lighter olefins, disproportionating propylene produced by the first step to ethylene and butenes, alkylating the butenes with isobutane, catalytically reforming a C5+ fraction from the first step, and recombining the alkylate and reformate with unconverted gasoline fractions to form the higher octane gasoline.

United States Patent Banks Oct. 2, 1973 INCREASING THE OCTANE OF OLEFINIC GASOLINES USING DISPROPORTIONATION, ALKYLATION AND REFORMING STEPS [75] Inventor: Robert L. Banks, Bartlesville, Okla.

[73] Assignee: Phillips Petroleum Company,

Bartlesville, Okla.

[22] Filed: Dec. 10, 1971 [21] Appl. No.: 206,735

3,409,540 11/1968 Gould et al. 208/79 3,060,116 10/1962 Hardin et al 1 208/79 3,071,535 1/1963 Condrasky et al 208/79 3,650,943 3/1972 Schuller 208/79 3,634,538 l/l972 Steffgen 260/683 Primary ExaminerDelbert E. Gantz Assistant Examiner-C. E. Spresser AttorneyYoung & Quigg [57] ABSTRACT A process for converting an olefinic gasoline to a higher octane value gasoline comprises the steps of subjecting the feed gasoline, or a fraction thereof, to olefin disproportionation in the presence of added ethylene to convert some of the heavier olefins to lighter olefins, disproportionating propylene produced by the first step to ethylene and butenes, alkylating the butenes with isobutane, catalytically reforming a C fraction from the first step, and recombining the alkyl- [56] References Cited ate and reformate with unconverted gasoline fractions UNIT STATES PATENTS to form the higher octane gasoline.

3,565,969 2/1971 Hutto et al 260/683 7 Claims, 1 Drawing Figure ETHYLENE7 I 5C4 2 i & a l2 16 I6 2 2] l3 E w c i 5 3 N C ED 222033; 5 1 g j l N w "z z 3 5 5i 5: g 22 N HIGH OCTANE 5 5 & GASOUINE L O 23 E m 1 5 E '5 t O m FUEL GAS 7 l l INCREASING THE OCTANE OF OLEFINIC GASOLINES USING DISPROPORTIONATION, ALKYLATION AND REFORMING STEPS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the process of upgrading gasolines containing olefinic hydrocarbons to provide a gasoline having a higher octane value. The invention also relates to the combination of process steps including those of disproportionation, alkylation, and catalytic reforming to provide gasolines having higher octane values. I

2. Description of Art Prior ARt The reaction of olefinic materials to produce other olefinic materials wherein the reaction can be visualized as the breaking of two existing double bonds between first and second carbon atoms, and between third and fourth carbon atoms, respectively, and the formation of two new double bonds, such as between the first and second carbon atoms and the second and fourth carbon atoms, respectively, and wherein the two new double bonds can be on the same or different molecules, has been called the olefin reaction." The breaking and formation of these bonds can be visualized by using a mechanistic scheme involving a cyclobutane transition state. Thus, two unsaturated pairs of carbon atoms combine to form a 4-center (cyclobutane) transition state which then disassociates by breakingeither set of opposing bonds. This reaction can be illustrated by the following formulas:

Other terms have been utilized to describe the reactions of olefinic materials which are within the scope of the olefin reaction as defined above. These include such terms as olefinic disproportionation, olefin dismutation, transalkylidenation," and olefin metathesis. Throughout the specification and claims the term olefin disproportionation is used as a matter of choice and is deemed to be equivalent to the abovementioned terms, including the olefin reaction" terminology. Numerous catalyst systems have been reported which effect this reaction, including the catalysts of U.S. Pat. No. 3,261,879, Banks, (I966), and US. Pat. No. 3,365,5l3, Heckelsberg (I968).

One important aspect of the olefin disproportionation reaction is the embodiment wherein a mixture of ethylene and higher olefins is disproportionated. The presence of ethylene in the reaction mixture changes the nature of the olefinic products such that most, if not all, of the olefins converted are converted to other olefins having a smaller number of carbon atoms. Such a result has been termed ethylene cleavage" or etheneolysis. Thus, higher olefins such as hept enes, octenes, decenes, etc., can be converted to lower olefins such as propylene, and butenes. This result is sometimes promoted by the presence of double bond isomerization activity within the reaction zone.

Recently, the oil industry has been faced with the I problem of upgrading the octane values of gasolines produced in standard refinery operations. This problem has its genesis in the additional problem brought upon the heavily industrialized countries because of pollution of the atmosphere by automobile exhaust emissions. Technological development. in the prevention of air pollution caused by the internal combustion engine has resulted in curtailing the use of lead compounds in gasoline; This was necessitated by the proposed use of catalytic mufflers which employ conversion catalysts which are sensitive to lead compounds in automobile emissions.

Accordingly, the producers of gasolines for automobile engines have been required to increase the octane value of their refinery gasolines to meet the high performance requirement of the modern internal combustion engine without the assistance of added alkyllead compounds.

OBJECTS OF THE INVENTION It is an object of this invention to upgrade olefinic gasolines to gasolines having higher-octane values. Other objects and advantages of the invention will be apparent to those skilled in the art from the following summary of the invention, detailed description of the invention and the claims.

SUMMARY OF THE INVENTION My invention comprises the utilization of a combination of steps to provide a higher octane gasoline. The combination of steps employed includes olefin disproportionation, alkylation, and catalytic reforming. According to my process, a gasoline containing at least about 20 weight percent olefins is first subjected to conversion in an olefin disproportionation zone in the presence of added ethylene. The olefin disproportionation conversion of ethylene and the olefinic gasoline causes the heavier olefins within the gasoline to be converted to lighter olefins including ethylene, propylene, and butenes. The effluent from this first disproportionation zone is then conducted to a separation Zone wherein propylene, butenes and a C hydrocarbon fraction can be separated from the effluent. The separated propylene fraction is then passed to a second olefin disproportionation zone wherein it is converted to ethylene and butenes. The ethylene and butenes which are produced in the second olefin disproportionation step are then passed to the separation zone. The C hydrocarbon fraction which is removed from the separation zone is passed to a catalytic reforming zone wherein, in the presence of hydrogen, it is converted to a catalytic reformate. Butenes which are separated from the separation zone are c-onductedto an alkylation zone wherein they are alkylated with isobutane to provide a high octane alkylate. The reformate and the alkylate are then combined in the final step of my process to provide the high octane gasoline.

BRIEF DESCRIPTION OF THE DRAWING The sole FIGURE of the drawing presents a simplified schematic flow diagram of my process.

DETAILED DESCRIPTION OF THE INVENTION The starting material for the process of my invention I is an olefinic containing gasoline having at least about 10 weight percent of olefin hydrocarbons. The gasoline will preferably have an end point which does not exceed about 450F. Preferably, the olefinic gasoline contains about 30 to about 70 weight percent olefin hydrocarbons. Such streams are readily available as a product of a catalytic cracker. Preferably, the feed to my process is a full range cat-cracked gasoline. If desired, the catalytically cracked gasoline can be fractionated to provide suitable fractions which are high in olefin content. That is, the full range cat-cracked gasoline can be fractionated to provide a product stream which is richer in olefins and paraffins by reducing the aromatic content of the material. The olefin rich material is then employed in my process.

The process of my invention has the following unique advantages: (a) it provides a high octane gasoline which has a reduced olefinic content with corresponding increase in the MON-clear octane value; (b) it provides a general increase in road octane value; and (c) it generally provides a greater volume of high octane gasoline than the volume of the catalytically cracked gasoline feed material.

The above-mentioned advantages of the invention can best be understood by reference to the drawing which depicts a simplified schematic flow scheme of my process. Briefly, a full range cat-cracked gasoline, or a light or heavy fraction of a full range cat-cracked gasoline can be passed via line 11 into a disproportionation zone 2. Ethylene, in line 12, is introduced into the disproportionation zone via line 13. Within disproportionation zone 2 the linear and branched olefins within the cat-cracked gasoline feed undergo reaction (cleav age) with ethylene to provide lighter olefinic products including ethylene, propylene, butenes, and C olefins. The effluent from the disproportionation zone 2 is passed via line 14 into separation zone 4. If desired, any unconverted higher olefins can be recycled from separation zone 4 to disproportionation zone 2. However, it is preferred that the conditions in zone 2 be sufficiently severe (low space rate, high ethylene ratio, etc.) to convert substantially all of the cleavable olefins in one pass.

Within separation zone 4, the ethylene is separated and removed via line 18 for return to disproportionation zone 2 via line 13. Propylene is removed from separation zone 4 via line 16 and passed to disproportionation zone 3. Butenes are removed from separation zone 4 via line 19 and passed to alkylation zone 6. The C material is removed from line 23 and passed to the catalytic reforming zone 7. Within olefin disproportionation zone 3, propylene from line 16 undergoes the disproportionation reaction to provide additional ethylene and butenes. The effluent is removed from reactor zone 3 and passed via line 17 into line 14 and returned to the separation zone. This step provides additional butenes for alkylation zone 6 as well as additional ethylene for use in the first disproportionation zone 2.

Within alkylation zone 6, the butenes produced in both disproportionation zones 2 and 3 are alkylated with isobutane using a suitable alkylation catalyst and conditions. The alkylation of the butenes with isobutane provides a high octane alkylate which is withdrawn via line 22.

The C material withdrawn from separation zone 4 via line 23 is very low in olefin content and is especially suitable for catalytic reforming. The C material within zone 7 is contacted with hydrogen introduced via line 27 in the presence of a suitable reforming catalyst under suitable reaction conditions which provide a high octane catalytic reformate that is removed from zone 7 via line 24. Light paraffinic materials which are produced within the catalytic reforming zone such as 5 methane, ethane, etc. is withdrawn from the zone via line 28 for use as fuel gas. The reformate is removed by way of line 24. It is sometimes desirable that prior to contact with the reforming catalyst, the C material be subjected to mild hydrotreatment with a suitable catalyst. The high octane alkylate and the high octane reformate can then be combined in line 26 for recovery as a high octane gasoline product of the process.

Within olefin disproportionation zone 2, the catalytic material which may be employed may be any suitable olefin disproportionation catalyst, capable of converting propylene to ethylene and butenes. Solid catalysts are preferred. These catalysts are well known in the prior art. Of particular usefulness are catalysts such as molybdenum oxide on alumina, tungsten oxide on silica, rhenium heptoxide on alumina, tungsten oxide on aluminum phosphate and the like. These catalysts have high activity for the conversion of olefinic materials in the presence of ethylene to provide lighter olefinic products.

These solid olefin disproportionation catalysts can advantageously be combined with a solid olefin double bond isomerization catalyst to provide increased conversion of the gasoline olefin fraction to the desired butenes. A particularly suitable catalyst for this purpose is magnesium oxide, although other suitable solid double bond isomerization catalysts such as zinc oxide, alumina, and the like, can be used. The isomerization catalyst and the disproportionation catalyst are preferably used as a mixed catalyst bed in which the amount of isomerization catalyst is from about 2:1 to 10:1 parts by weight per part of the disproportionation catalyst.

The particular conditions utilized in the first olefin disproportionation zone will be dependent upon the particular olefin disproportionation catalyst employed and thus can vary in a wide range. Choices of particular operating conditions are well known to those skilled in the olefin disproportionation art. Depending upon the specific disproportionation catalyst, a temperature in the range of 60 to 1,200 F. can be employed. Pres- Disproportionation Temperature "F.

Catalyst Broad Preferred WOJSiO, 400-l 100 600-900 MoOJSiO, 400-1 I00 800-l 000 Moog/n.0, 150-5 00 250-400 WOJAhO; 100-750 550-650 Re,O,/Al,0 l000 I00-500 WO /AlPO, 600-] 200 800-l 000 60 Re,O-,/AlPO 60-l000 50-250 MOOJAlPO 600-1200 800-1000 Because of its high level of activity and durability, the WO /Si0 catalyst is presently preferred for this reaction zone.

In the olefin disproportionation zone 2, the molar ratio of ethylene to other olefins can be in the range of 2-20, preferably 2-10.

sures in the range from 0 to 2,000 psig are suitable al- In my work 1 have observed that not all cat-cracker gasolines can be converted in an olefindisproportionation zone with equal effectiveness. The reason for this phenomenon is not completely understood; however, it is believed that the presence of sulfur and/or oxygen components within the cat-cracked gasoline may exert a deleterious effect upon the effectiveness of the olefin disproportionation catalyst. Accordingly, it may sometimes be desirable to subject the cat-cracked gasoline to a mild hydrotreatment prior to introduction into the first olefin disproportionation zone. A suitable catalyst for the mild hydrotreatment can be a sulfided nickelalumina catalyst at an operating temperature of 550 F. with a pressure of 150 psig. However, other suitable hydrotreating catalysts and conditions can be employed.

The second olefin disproportionation zone employed in my process for the conversion of propylene to butenes and ethylene can use the same olefin disproportionation catalyst as employed in the first olefin disproportionation zone. Once again, the temperatures, pressures, reaction times and various other conditions within the second olefin disproportionation zone will depend upon the specific olefin disproportionation catalyst employed. However, the temperatures and pressures and contact times, etc., would generally fall within the ranges described above for the first olefin disproportionation zone.

The alkylation zone can employ any suitable alkylation catalyst using known alkylation conditions to pro vide a high octane alyklate. A suitable catalyst is hydrofluoric acid at a temperature of 80l00 F., a contact time of 1-l0 minutes, and a suitably high isobutane ratio (e.g. 6-15 mols per mol of olefin). The high oc tane alkylate produced in the process is a C containing stream having a high percentage of paraffins which is virtually free of olefins, but does contain some naphthenes and aromatics.

In the catalytic reforming step of my process, there is provided a suitable reforming catalyst, preferably a platinum-containing catalyst comprising platinum deposited on a cracking catalyst such as silica-alumina or psig, preferably 50-750 psig. Any suitable reforming catalyst and process can be used.

It is to be understood by those skilled in the art that the above-described description of the process of the invention has omitted detailed description of the apparatus or other. instrumentation which can be used to carry out the process of the invention. However, the design of the apparatus used to implement the process ofmy invention is readily within the skill of those in the art.

My invention can further be understood by reference to the 'followingexample which is presented to illustrate the process of the invention. However, the particular details which are set forth therein should not be construed to unduly limit the invention as described hereinabove.

EXAMPLE I In accordance with the schematic flow diagram ofthe drawing, a catalytically cracked gasoline is subjected to the process of my invention as follows. The cat-cracked gasoline is a 200F to 425F boiling range material with an AP] gravity of 39.3 and a Research Octane No. (RON clear of 90.5 and a motor octane No. (MON) clear of 79.4. The cat-cracked gasoline contains about 35 wt. of olefinic hydrocarbons.

" Olefin disproportionation zone 2 is an olefinic disproportionation reactor containing 4,000 pounds of an olefin disproportionation catalyst comprising 8 wt. tungsten oxide and 92 wt. Si0 mixed with 28,000 pounds of a magnesia double bond isomerization catalyst. Operating conditions in the reactor include a temperature of 750F and a pressure of 325 psig, and a WHSV of about40. The molar ratio of ethylene to olefins in the reactor is maintained at about 4:1.

Olefin disproportionation zone 3 is an olefin disproportionation reactor containing 11,300 pounds of 8 wt. WO -92 wt. Sillolefin disproportionation catalyst. Operating conditions include a temperature of 725F and a pressure of 325 psig, and WHSV of about 30.

The alkylation zone 6 is a conventional HF alkylation unit using HF catalyst. The conditions with the unit include a temperature of F, a pressure of psig, a HF/hydrocarbon volume ratio of 1:1 and a contact time of about 3 minutes. The alkylate from the unit has an RON-clear of 97.5 and a MON-clear of 94.3.

The reforming zone 7 is a conventional catalytic reforming unit using alumina promoted by 0.33 wt. platinum, 0.41 wt. fluoride, and 0.33 wt. chloride. Reaction conditions include a temperature of 925F, 500 psig pressure, and 2.0 WHSV.

The process is illustrated by the following material balance in Table I.

TABLE I Stream Number 11 12 14 16 17 18 19 21 22 23 24 26 Olefin component, lbs/hour:

C3- 16, 500 39,400 22, 900 06-. 8, 200 10 600 i c i 66. 700 62, 300 102, 900

Total 81, 200

NOTE.-The above table shows that the process of the invention is capable ot converting 81,200 pounds per hour of cat-cracked gasoline and 4,800 pounds per hour ethylene into 102,000 pounds per hour of gasoline having a higher octane value.

The octane values of the various streams are given below in Table ll.

TABLE ll Octane Ratings Clear lream Research Motor 1 90.5 79.4 9 97.5 94.3 ll 94.3 84.5 12 95.5 89.2

it can be seen from the above Table II that the process of the invention gives a significant increase in octane values over the original catcracked gasoline feed material. in addition, the volume of gasoline in line 26 is ificrea sed about 25% based on its initial olefin content.

Reasonable variations and modifications of my invention will be apparent to those skilled in the art without departing from the spirit and scope of my invention.

I claim:

1. A process of increasing theoctane value of a gasoline boiling range feed stream containing at least about 20 weight percent olefinic hydrocarbons comprising the steps of:

l. passing the gasoline and sufficient ethylene to provide a molar ratio of ethylene to other olefins in the range of 2-20 to a first olefin disproportionation zone thereby converting at least some of the heavier olefins in the gasoline to lighter olefins including propylene and butenes;

2. passing the effluent from the first disproportionation zone to a separation zone wherein propylene is removed therefrom, a butenes stream is removed, and a fraction containing C hydrocarbons is removed;

3. passing the propylene streaiirto a second olefin disproportionation zone to provide additional ethylene and butenes;

4. passing the effluent from the second disproportionation zone to the separation zone;

5. passing the butenes stream from the separation zone to an alkylation zone wherein the butenes are alkylated with isobutane to provide an alkylate;

6. passing the C hydrocarbon stream to a catalytic reforming zone to provide a reformate,

7. whereby the reformate and alkylate when combined provide a gasoline boiling range material having an increased octane value.

2. The process of claim I, wherein the olefinic gasoline is a catalytically cracked gasoline having from about 30 weight percent to about weight percent olefin hydrocarbons.

3. The process of claim 1 wherein the C hydrocarbon fraction is hydrotreated prior to being subjected to catalytic reformation in step 6.

4. The process of claim 1 wherein the olefinic containing gasoline is a fraction obtained from the fractionation of a full range cat-cracked gasoline.

5. The process of claim 1 wherein the ethylene produced in step 3 is recovered from the separation zone and returned to the first olefin dis-proportionation zone.

6. The process of claim 1 wherein the olefinic gasoline is subjected to a mild hydro treatment prior to being passed into the first olefin disproportionation zone.

7. The process of claim 1 wherein the reformate and alkylate are combined to provide a gasoline boiling range material having an increased octane value. 

2. The process of claim 1, wherein the olefinic gasoline is a catalytically cracked gasoline having from about 30 weight percent to about 70 weight percent olefin hydrocarbons.
 2. passing the effluent from the first disproportionation zone to a separation zone wherein propylene is removed therefrom, a butenes stream is removed, and a fraction containing C5+ hydrocarbons is removed;
 3. passing the propylene stream to a second olefin disproportionation zone to provide additional ethylene and butenes;
 3. The process of claim 1 wherein the C5+ hydrocarbon fraction is hydrotreated prior to being subjected to catalytic reformation in step
 6. 4. The process of claim 1 wherein the olefinic containing gasoline is a fraction obtained from the fractionation of a full range cat-cracked gasoline.
 4. passing the effluent from the second disproportionation zone to the separation zone;
 5. passing the butenes stream from the separation zone to an alkylation zone wherein the butenes are alkylated with isobutane to provide an alkylate;
 5. The process of claim 1 wherein the ethylene produced in step 3 is recovered from the separation zone and returned to the first olefin dis-proportionation zone.
 6. The process of claim 1 wherein the olefinic gasoline is subjected to a mild hydro treatment prior to being passed into the first olefin disproportionation zone.
 6. passing the C5+ hydrocarbon stream to a catalytic reforming zone to provide a reformate,
 7. whereby the reformate and alkylate when combined provide a gasoline boiling range material having an increased octane value.
 7. The process of claim 1 wherein the reformate and alkylate are combined to provide a gasoline boiling range material having an increased octane value. 